EOL_HF

EOL Raw data: January 2018 to December 2022

Gaps:

  • 21 Mar to 17 May 2019.
  • 22 to 24 Nov 2022

NAs:

  • No NAs for T
  • NAs for S, O, AOU

Anomalies method

By months

Time series anomaly regression analyses per month
Slope SE Slope P Slope Intercept SE int. P int. F df R2 P value
temp_ano 0.0322404 0.0040676 0 -65.14189 8.218505 0 62.8254 39938 0.0015706 0
sal_ano 0.0263224 0.0007535 0 -53.18294 1.522422 0 1220.3225 39008 0.0303349 0
oxy_ano -1.4649535 0.0270565 0 2959.86194 54.666168 0 2931.6077 39007 0.0699024 0
aou_ano 1.3467183 0.0230785 0 -2720.97387 46.628895 0 3405.1692 39007 0.0802876 0

Temperature

Salinity

Oxygen

AOU

By days

Time series anomaly regression analyses per day
Slope SE Slope P Slope Intercept SE int. P int. F df R2 P value
temp_ano_day 0.0338983 0.0030054 0 -68.49171 6.072406 0 127.2198 39938 0.0031753 0
sal_ano_day 0.0250891 0.0006957 0 -50.69120 1.405572 0 1300.6450 39008 0.0322671 0
oxy_ano_day -1.4609430 0.0241975 0 2951.75892 48.889779 0 3645.2375 39007 0.0854642 0
aou_ano_day 1.3550905 0.0222610 0 -2737.88944 44.977167 0 3705.5087 39007 0.0867546 0

Temperature

Salinity

Oxygen

AOU

Results from anomaly methods (month and day) are similars with a slight improvement in SD.

Other methods:

By autocorrelation + decompose function or Mann-Kendall : not possible because of gaps

–> Filling gaps.

Moving average

Temperature

No gaps to fill.

## 
## Call:
## lm(formula = y ~ x, data = reg_val_ts_temp_eol_less_season)
## 
## Residuals:
##      Min       1Q   Median       3Q      Max 
## -11.2904  -2.1147  -0.1173   1.5592  10.5261 
## 
## Coefficients:
##             Estimate Std. Error t value Pr(>|t|)    
## (Intercept) 18.49114    0.04911  376.51   <2e-16 ***
## x            0.18173    0.01390   13.07   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.655 on 39938 degrees of freedom
## Multiple R-squared:  0.004259,   Adjusted R-squared:  0.004234 
## F-statistic: 170.8 on 1 and 39938 DF,  p-value: < 2.2e-16

Slope is 0.182. Means that periode of 5 years is not suitable. Slope not reliable.

Salinity

## 
## Call:
## lm(formula = y ~ x, data = reg_val_ts_sal_eol_less_season)
## 
## Residuals:
##      Min       1Q   Median       3Q      Max 
## -3.02197 -0.12426  0.03126  0.14767  0.53884 
## 
## Coefficients:
##              Estimate Std. Error  t value Pr(>|t|)    
## (Intercept) 3.791e+01  2.440e-03 15532.81   <2e-16 ***
## x           1.005e-04  2.432e-06    41.31   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 0.2436 on 39938 degrees of freedom
## Multiple R-squared:  0.04098,    Adjusted R-squared:  0.04095 
## F-statistic:  1706 on 1 and 39938 DF,  p-value: < 2.2e-16

Slope is 0. Means that periode of 5 years is not suitable. Slope not reliable.

Oxygen

## 
## Call:
## lm(formula = y ~ x, data = reg_val_ts_oxy_eol_less_season)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -65.320 -15.280   1.126  15.024  44.776 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  2.417e+02  1.852e-01 1305.08   <2e-16 ***
## x           -7.905e-03  1.846e-04  -42.82   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 18.49 on 39938 degrees of freedom
## Multiple R-squared:  0.0439, Adjusted R-squared:  0.04388 
## F-statistic:  1834 on 1 and 39938 DF,  p-value: < 2.2e-16

Slope is -0.008. Means that periode of 5 years is not suitable. Slope not reliable.

AOU

## 
## Call:
## lm(formula = y ~ x, data = reg_val_ts_aou_eol_less_season)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -34.302  -6.017   0.323   6.586  38.208 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept) -1.348e+01  8.602e-02 -156.74   <2e-16 ***
## x            3.861e-03  8.572e-05   45.05   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 8.588 on 39938 degrees of freedom
## Multiple R-squared:  0.04835,    Adjusted R-squared:  0.04833 
## F-statistic:  2029 on 1 and 39938 DF,  p-value: < 2.2e-16

Slope is 0.004. Means that periode of 5 years is not suitable. Slope not reliable.

Mann-Kendall

  • The function kendall.SeasonalTrendTest returns estimated values of Kendall’s τ, the slope, and the intercept for each season, as well as a single estimate for each of these three quantities combined over all seasons. The overall estimate of τ is the weighted average of the p seasonal τ’s

  • The overall estimate of slope is the median of all two-point slopes computed within each season.

  • The overall estimate of intercept is the median of the p seasonal estimates of intercept.

  • The Kendall Tau, or Kendall rank correlation coefficient, measures the monotony of the slope. Kendall’s Tau varies between -1 and 1; it is positive when the trend increases and negative when the trend decreases.

  • The Sen slope, which estimates the overall slope of the time series. This slope corresponds to the median of all the slopes calculated between each pair of points in the series.

  • The significance, which represents the threshold for which the hypothesis that there is no trend is accepted. The trend is statistically significant when the p-value is less than 0.05.

Results:

Temperature

##         tau       slope   intercept 
##  0.04282142  0.04045000 36.35810833

Salinity

##         tau       slope   intercept 
##   0.1023034   0.0199750 -27.4444783

Oxygen

##         tau       slope   intercept 
##  -0.1107562  -1.1655297 732.7343833

AOU

##           tau         slope     intercept 
##     0.1704564     1.5167524 -2653.5551529

Results from Mann-Kendall and anomalies (by day) are similars.